Flocculi

Flocculi is the plural form of flocculus, a term used in anatomy to describe small, tuft-like lobes or lobules found in various structures. The most well-known example is the cerebellar flocculus, a paired, rounded lobe on the inferior surface of each cerebellar hemisphere. The cerebellar flocculi are part of the vestibulocerebellum, together with the nodulus, and play a key role in balance and eye movement control.

In the cerebellum, each flocculus receives input from the vestibular system via the vestibular nuclei and integrates signals related to head motion. It helps regulate the vestibulo-ocular reflex (VOR), which stabilizes gaze during head movement, and participates in the adaptation of this reflex to changing circumstances. The flocculus communicates with other cerebellar circuitry through Purkinje cells, receiving mossy fiber inputs from vestibular pathways and climbing fiber inputs that convey error signals from the inferior olive.

Clinically, dysfunction or damage to the vestibulocerebellar system, including the flocculi, can cause vestibulocerebellar syndrome. Typical signs include truncal and gait ataxia, a wide-based stance, vertigo, head tilting, and nystagmus. Such features reflect impaired gaze stabilization and balance rather than limb coordination deficits.

Beyond the cerebellum, the term flocculus can be used in zoological or anatomical descriptions to denote similar small tufted lobes in other organs or species, but the cerebellar flocculus remains the most prominent and widely referenced example.